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Author Topic: DynamicPSF question  (Read 2174 times)

Offline CraigNZ

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DynamicPSF question
« on: 2016 February 02 19:59:29 »
When "Moffat" is selected, what beta parameters are tested?  Does it do some sort of range test and narrow in on a best beta by comparing MAD results?

Also, if "Auto" is selected, how does it select the beta parameter, also by searching?

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Offline Juan Conejero

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Re: DynamicPSF question
« Reply #1 on: 2016 February 03 00:28:09 »
When the Moffat and Auto model functions are selected, DynamicPSF fits the beta parameter with the Levenberg-Marquadt algorithm. Note that this is not a search procedure; beta is fitted just as A, B, cx, cy, sx and sy (and r and theta when fitting an elliptic function).

In Auto mode, the process fits Gaussian and variable-beta Moffat functions, then selects the model with the least residual.
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Juan Conejero
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Offline CraigNZ

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Re: DynamicPSF question
« Reply #2 on: 2016 February 03 13:09:26 »
So if I got this right, Moffat (or Auto) will try a few beta values and then do a Levenberg-Marquadt algorithm (least squares fit) of the values to derive the optimal beta value?
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